$(function () {
    var bgCounter = 0;
    $(".toggle_bg").click(function () {
        backgrounds = [
            "img/shu.jpg",
            "img/gta1.jpg",
            "img/gta2.jpg",
            "img/gta3.jpg",
            "img/gta4.jpg",
            "img/gta5.jpg"
        ];
        function changeBackground() {
            bgCounter = (bgCounter + 1) % backgrounds.length;
            $('body').css('background', '#000 url(' + backgrounds[bgCounter] + ') no-repeat');
            $('body').css('backgroundSize', 'cover');
        }
        changeBackground();
    })
})